This invention relates to tamper evident safety closures for containers of a general type as e.g. disclosed in U.S. Pat. Nos. 4,527,701 and 4,555,036. Such closures have two caps, one, a so called inner cap, to be screwed onto a container to be closed and the other one, a so called outer cap, in which the inner cap is housed. The caps have a top wall and a skirt at the outer periphery thereof, the skirt of the outer cap surrounding the skirt of the inner cap. Spring means urge the caps axially apart and retaining means limit such separating movement. Cam or ratchet means allow the caps to rotate in one direction with respect to each other, whereas on rotation of the outer cap in the opposite direction the inner cap is rotated with the outer cap by the cam of ratchet means. Axial depression of the outer cap towards the inner cap against the spring means brings parts of the cam or ratchet means in cooperation, that make rotation of the outer cap in said one direction cause rotation of the inner cap with the outer cap. These directions are chosen in relation to the direction of screw-threading the inner cap onto the container so that the closure can be screwed onto the container with its inner cap by rotating the outer cap without depressing it towards the inner cap, while screwing the closure off from the container can only take place after such depressing. This makes the closure safe in the hands of children, which cannot open the container as this requires a depression of the outer cap before the closure can be screwed off therefrom.
It is moreover known from said U.S. patent specifications to provide the inner cap with a central upwardly protruding part and to provide the top wall of the outer cap with a central opening, which is bridged by a bridging wall portion, connected by a rupturable connection to said top wall, so that, on depressing the outer cap for the first time, said protruding part of the inner cap ruptures said connection to separate the bridging wall portion from the outer cap. This makes it visible at once that the outer cap has been depressed, so that the closure may have been tampered with.
Closures with such rupturable bridging wall portions have, however, several disadvantages, one being that it may be put and pushed back in place, so that tampering is not immediately evident, the other one being that the bridging wall portion may be propelled away on rupturing of the connection, may get lost, swallowed by children, fall into foodstuffs or hit the eye of a person or such disadvantage. It has thus been proposed in said U.S. Pat. No. 4,527,701 to apply not only a rupturable connection, but also at least one non rupturable connection between said bridging wall portion and the top end wall of the outer cap. Although this may remove the said second disadvantage, it will not remove the first one, in particular not if the non rupturable connection is a thin curved bridge part being easily deformable to allow some upward movement of the bridging wall portion with respect to the top end wall of the outer cap, as it will also allow downward movement of said bridging wall portion thereafter, back again to its original shape and position, in which this connection is mainly out of sight below the top end wall of the bridging wall portion.